1. Filed of the Invention
The present invention relates to a vehicular active drive assist system which makes a proper judgment on the possibility of deviation of own vehicle from a traffic lane and, if there exists the possibility of deviation from the traffic lane, generates a warning to assist a driver in driving.
2. Description of the Related Art
A comprehensive active drive assist system (ADA system) which actively assists a driver in driving operations has been developed in recent years. This ADA system estimates the possibility of various incidences, such as a collision with a vehicle running ahead, contact with an object and deviation from a traffic lane, from information on vehicle driving environments or running state of own vehicle and, when it is predicted that safety can not be maintained, alerts the driver or otherwise performs control operation.
While a laser radar system, for instance, has conventionally been known as a device for obtaining the aforementioned vehicle driving environment information, Japanese Patent Laid-Open No. 265547/1993 covering an application filed by the present applicant proposes an approach to obtaining three-dimensional recognition of a road and traffic environments with practically sufficient accuracy and promptness by processing information on images of scenery and objects ahead of the vehicle captured by a plurality of cameras installed onboard.
Prevention of deviation from a traffic lane, one of functions of the aforementioned ADA system, is intended to alert the driver to an extremely close approach to or crossing of a lane marking by producing a warning, for instance, should such a situation occur, and thereby help prevent traffic accidents which might be caused by a lack of attention, dozing, failure to watch ahead, or other behavior related to the driver""s carelessness. Various proposals have already been made with respect to this lane deviation preventing function.
In the aforementioned lane deviation preventing function, one method of judging deviation of own vehicle from a traffic lane, for example, is such that a judgment line parallel to a lateral direction of the own vehicle is set ahead of the own vehicle, the position (lateral position) of the own vehicle and the positions of lane markings on the judgment line are compared, and it is judged that there is a possibility of deviation from the traffic lane if the positions of the lane marker lines does not exist outside the position of the own vehicle. If, however, a roadway has a complicated winding shape forming an S-shaped curve, for instance, there is a possibility of an increased frequency of misjudgments. For example, while there is no possibility of deviation from the traffic lane at a curve immediately ahead if the own vehicle continues to run in its current running state, the judgment line may be set on a curve farther ahead. In this case, a judgment on deviation from the traffic lane would be made on this judgment line, and a misjudgment may be made that there is a possibility of deviation from the traffic lane.
This invention has been made in consideration of the foregoing circumstances. Accordingly, it is an object of the invention to provide a vehicular active drive assist system which takes into consideration a complicated curve ahead, should it exist, and can make an accurate judgment on the possibility of deviation from a traffic lane.
To achieve the aforementioned object, a vehicular active drive assist system according an embodiment of this invention comprises a lane deviation judgment unit which judges the possibility of deviation of own vehicle from a traffic lane on a roadway ahead and a warning control unit which controls a warning based on judgment results fed from the lane deviation judgment unit, the vehicular active drive assist system being characterized in that the lane deviation judgment unit sets a first judgment line approximately parallel to a lateral direction of the own vehicle at a first distance ahead of the own vehicle, sets a second judgment line approximately parallel to the lateral direction of the own vehicle at a second distance ahead of the own vehicle, makes a judgment on the possibility of deviation from the traffic lane based on the location of the own vehicle and the location of lane markings on the first judgment line, makes another judgment on the possibility of deviation from the traffic lane based on the location of the own vehicle and the location of the markings on the second judgment line, and finally judges the possibility of deviation from the traffic lane based on the results of these two judgments. As a result, it is possible to make an accurate judgment on the possibility of deviation from the traffic lane even when there is a complicated curve ahead.
The vehicular active drive assist system according to the embodiment of this invention further comprises a vehicle speed sensing unit for detecting vehicle speed, wherein the lane deviation judgment unit variably sets positions of the own vehicle on the first judgment line and the second judgment line to be used in judging the possibility of deviation from the traffic lane according to the vehicle speed. Thus, consideration is given to the fact that the seriousness of deviation from the traffic lane varies with the vehicle speed, for instance, and this is reflected in the judgment results so that the system provides higher accuracy and greater practicability.
Further, in the vehicular active drive assist system according to the embodiment of this invention, it is preferred that the lane deviation judgment unit sets a left side judgment value and a right side judgment value differing from each other in size as positions of the own vehicle. This makes it possible to judge the possibility of deviation from the traffic lane in a manner compatible with a driver""s recognition of vehicle width.